Delta Tau PMAC2A-PC/104 Handwheel Encoder Termination Resistors, Device Resistor Pack Pack Size

PMAC2A PC104 Hardware Reference Manual

The ‘-‘ inputs of each differential pair each have a hard-wired 2.2 kΩ resistor to +5V; each also has another 2.2 kΩ resistor as part of a socketed resistor pack that can be configured as a pull-up resistor to +5V, or a pull-down resistor to GND.

If this socketed resistor is configured as a pull-down resistor (the default configuration), the combination of pull-up and pull-down resistors on this line acts as a voltage divider, holding the line at +2.5V in the absence of an external signal. This configuration is required for single-ended inputs using the ‘+’ lines alone; it is desirable for unconnected inputs to prevent the pick-up of spurious noise; it is permissible for differential line-driver inputs.

If this socketed resistor is configured as a pull-up resistor (by reversing the SIP pack in the socket), the two parallel 2.2 kΩ resistors act as a single 1.1 kΩ pull-up resistor, holding the line at +5V in the absence of an external signal. This configuration is required if complementary open-collector drivers are used; it is permissible for differential line-driver inputs.

If Pin 1 of the resistor pack, marked by a dot on the pack, matches Pin 1 of the socket, labeled by a white square, then the pack is configured as a bank of pull-down resistors. If the pack is reversed in the socket, it is configured as a bank of pull-up resistors. The following table lists the pull-up/pull-down resistor pack for each input device:

Device	Resistor Pack	Pack Size
Encoder 1	RP30	6-pin
Encoder 2	RP31	6-pin
Encoder 3	RP36	6-pin
Encoder 4	RP37	6-pin
Handwheel Encoder	RP55	6-pin

Handwheel Encoder Termination Resistors

The PMAC provides a socket for termination resistors on the handwheel encoder differential input pairs coming into the board. As shipped, there is no resistor pack in the RP56 socket. If these signals are brought long distances into the PMAC board and ringing at signal transitions is a problem, a SIP resistor pack may be mounted on the RP56 socket to reduce or eliminate the ringing. The 6-pin termination resistor pack is the type that has independent resistors (no common connection) with each resistor using 2 adjacent pins.

10 Acc-1P Hardware Setup